<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Title</title>
</head>
<body>

<script>
  // 断点 : 程序走到这 停了 之后 就可以查看 执行过的程序的执行结果
  let a = {x: 20};
  let b = a;
  debugger;
  a.x = 30;
  console.log(b);

  a.x = b = {x: 10};

  // a.x = b;
  // b = {x: 10};
  a.x.x = 40;
  console.log(b);

</script>
</body>
</html>
